A rain of ordinary chondritic meteorites in the early Ordovician

Schmitz, Birger; Tassinari, Mario; Peucker‐Ehrenbrink, Bernhard

doi:10.1016/s0012-821x(01)00559-3

Cited by 191 publications

(251 citation statements)

References 39 publications

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“…In summary, all inclusions plot within the L-chondritic field, which is in accordance with the previous classifications for the Ö sterplana fossil meteorites and the sediment-dispersed EC grains (Schmitz et al, 2001(Schmitz et al, , 2003Schmitz and Häggströ m, 2006;Bridges et al, 2007;Greenwood et al, 2007) as well as the revised classification of the Brunflo meteorite (Alwmark and Schmitz, 2008). The overall concordance in classification of the fossil meteorites and the sediment-dispersed grains with previous studies implies that the composition of inclusions of olivine and Ca-poor pyroxene in chromite from ordinary equilibrated chondrites can be used in determining meteorite group with no or very little overlap.…”

Section: Classification Of the Fossil Meteorites And The Origin Of Thsupporting

confidence: 91%

“…This is the first report on silicate inclusions in chromite from recent chondrites as well as in 470 Ma old fossil meteorites (Schmitz et al, 2001) and coeval sediment-dispersed chondritic chromite grains (Schmitz et al, 2003;Schmitz and Häggströ m, 2006). We demonstrate how these inclusions can be used for assessing the meteorite group from which the host chromite grain originates.…”

Section: Introductionmentioning

confidence: 69%

“…The samples are listed in Table 1. The Thorsberg quarry meteorites have previously been classified as L chondrites, based on their chromite element composition, chondrule sizes and in one case oxygen isotopic composition (Schmitz et al, 2001;Bridges et al, 2007;Greenwood et al, 2007). The Brunflo meteorite has formerly been assigned to the H-chondrite group (Thorslund et al, 1984), but a recent study by Alwmark and Schmitz (2008) shows that it belongs to the L group, founded, for example, on mean chondrule size.…”

Section: Methodsmentioning

confidence: 99%

“…The majority of studies on fossil meteoritic material focus on the Middle and Late Ordovician; a period where the meteorite influx to Earth was enhanced by up to two orders of magnitude (Schmitz et al, 2001). At 470 Ma the disruption of the L-chondrite parent body occurred (Anders, 1964;Korochantseva et al, 2007), and the high abundance of fossil meteoritic material in sediments from this time has been related to this event, based partly on the L-chondritic composition of relict chromite grains (Schmitz et al, 2001(Schmitz et al, , 2003Schmitz and Häggströ m, 2006).…”

Section: Introductionmentioning

confidence: 99%

“…At 470 Ma the disruption of the L-chondrite parent body occurred (Anders, 1964;Korochantseva et al, 2007), and the high abundance of fossil meteoritic material in sediments from this time has been related to this event, based partly on the L-chondritic composition of relict chromite grains (Schmitz et al, 2001(Schmitz et al, , 2003Schmitz and Häggströ m, 2006). Because meteoritic material on the Earth surface is rapidly altered or weathered away, with the exception of chromite (FeCr 2 O 4 ), constituting 0.05-0.5 wt% of recent chondrites (Keil, 1962), the classification of the fossil chondritic material in these studies has been based mainly on elemental and O-isotopic composition of chromite (e.g., Schmitz et al, 2001;Alwmark and Schmitz, 2007;Greenwood et al, 2007). Both these 0016-7037/$ -see front matter Ó 2008 Elsevier Ltd. All rights reserved.…”

Section: Introductionmentioning

confidence: 99%

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Relict silicate inclusions in extraterrestrial chromite and their use in the classification of fossil chondritic material

Alwmark

Schmitz

2009

Geochimica et Cosmochimica Acta

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Chromite is the only common meteoritic mineral surviving long-term exposure on Earth, however, the present study of relict chromite from numerous Ordovician (470 Ma) fossil meteorites and micrometeorites from Sweden, reveals that when encapsulated in chromite, other minerals can survive for hundreds of millions of years maintaining their primary composition. The most common minerals identified, in the form of small (<1-10 lm) anhedral inclusions, are olivine and pyroxene. In addition, sporadic merrillite and plagioclase were found.Analyses of recent meteorites, holding both inclusions in chromite and corresponding matrix minerals, show that for olivine and pyroxene inclusions, sub-solidus re-equilibration between inclusion and host chromite during entrapment has led to an increase in chromium in the former. In the case of olivine, the re-equilibration has also affected the fayalite (Fa) content, lowering it with an average of 14% in inclusions. For Ca-poor pyroxene the ferrosilite (Fs) content is more or less identical in inclusions and matrix. By these studies an analogue to the commonly applied classification system for ordinary chondritic matrix, based on Fa in olivine and Fs in Ca-poor pyroxene, can be established also for inclusions in chromite. All olivine and Ca-poor pyroxene inclusions (>1.5 lm) in chromite from the Ordovician fossil chondritic material plot within the Lchondrite field, which is in accordance with previous classifications. The concordance in classification together with the fact that inclusions are relatively common makes them an accurate and useful tool in the classification of extraterrestrial material that lacks matrix silicates, such as fossil meteorites and sediment-dispersed chromite grains originating primarily from decomposed micrometeorites but also from larger impacts.

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Section: Classification Of the Fossil Meteorites And The Origin Of Thsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 69%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Relict silicate inclusions in extraterrestrial chromite and their use in the classification of fossil chondritic material

Alwmark

Schmitz

2009

Geochimica et Cosmochimica Acta

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The Geochronology of Impact Craters

Kelley

Sherlock

2012

Impact Cratering

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Cosmic spherules from the Ordovician of Argentina

et al. 2012

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The discovery of magnetic spherules in acid‐insoluble residues from conodont samples encouraged a systematic search for Ordovician micrometeorites from northwestern Argentina. Some 220 melted micrometeorites were recovered from the magnetic fraction of six samples (total rock weight: 23 kg) from the Cordillera Oriental (Santa Rosita Formation) and 17 from five samples (total rock weight: 8.9 kg) from the Argentine Precordillera (Las Aguaditas, Gualcamayo and Las Vacas formations). The specimens resemble I‐type cosmic spherules, in their chemistry and distinct dendritic and polygonal crystalline structures. They represent a flux of micrometeorites several orders of magnitude greater than present. The wide differences in spherule abundance between the Precordillera and the Cordillera Oriental samples could reflect uncertainties in the sedimentary rates or temporal variations in the flux of extraterrestrial matter to Earth. The micrometeorite‐bearing formations span the late Tremadocian to the late Darriliwian (~480–460 Ma), which is consistent with a period of elevated flux of extraterrestrial material, as recorded several thousand kilometres away from coeval horizons in Scotland, Sweden and central China. Copyright © 2012 John Wiley & Sons, Ltd.

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A rain of ordinary chondritic meteorites in the early Ordovician

Cited by 191 publications

References 39 publications

Relict silicate inclusions in extraterrestrial chromite and their use in the classification of fossil chondritic material

Relict silicate inclusions in extraterrestrial chromite and their use in the classification of fossil chondritic material

The Geochronology of Impact Craters

Cosmic spherules from the Ordovician of Argentina

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